Bag machines



United States Ptent Donald C. Crawford;

Robert .1 Wech, Green Bay, Wisconsin [21] Appl. No. 787,767 [22] Filed Dec. 30, 1968 [45] Patented Nov. 24, 1970 [73] Assignec F M C Corporation San Jose, California a corporation of Delaware [72] lnventors [54] BAG MACHINES 16 Claims, 7 Drawing Figs.

[52] U.S. Cl ..93/33, 93/1, 93/584, 93/93 [51] Int. Cl B31b 1/20, B65b 65/08, B31b1/92 [50] Field of Search 93/1 (G), 33, All 58.4, 58.5, 58(.6), 93(C) [56] References Cited UNITED STATES PATENTS 3,146,147 8/1964 Naser 93/33(H) 3,240,091 3/1966 Gilbert 93/58(.6)

3,321,888 5/1967 Kirkhof 93/33(H-) 3,340,776 9/1967 Shabram 93/33(H) 3,355,996 12/1967 Medleycott 93/33(H) 3,384,528 5/1968 Lemacher 93/33(H) 3,431,828 3/1969 Crawford 93/93(C) 3,439,588 4/1969 Taylor 93/369 Primary Examiner-Wayne A. Morse, .lr. Attorneys-F. W. Anderson and C. E. Tripp ABSTRACT: The bag machine of the present disclosure comprises the usual heated reciprocating cutting and sealing bar which separates and welds a folded sheet of thermoplastic web into bags. A pneumatic cylinder, operated by a control circuit, moves a wedge shape block to prevent reciprocation of the seal bar by holding it in its raised position whenever the machine operator desires to interrupt web movement through the bag machine or when a predetermined number of bags have been produced.

Patented Nov. 24, 1970 Sheet INVENTORS DONALD 0.0RAWFORD ROBERT J. WECH ATTORNEYS h m M PE -Hi atented Nov. 24, 1970 3,541,929

ATTORNEYS Patented Nov. 24-, 1970 Sheet 5 014 D Ma 00 w Om AE ATTORNEYS r zz ze-l 226 WE'Q' 235.5%;

2.4-8 sssm fi 53% INVENTORS DONALD 0.6RAWFORD ROBERT J. WECH ATTORNEYS BAG MACHINES BACKGROUND OF THE INVENTION Presently available bag machines produce normal size bags at a rate of 150 to I70 bags per minute. The bags produced are discharged to a stacking table, which is usually provided with fences or abutments. WhlCh constrain the bags to stack in a neatly registered pile Various arrangements are available for producing overlapping or shingled stacks of bags with each stack containing a predetermined number of bags. For example. the stacking tables of some bag machines include an in dexing conveyor for supporting the stacks of bags and the degree to which the conveyor is indexed determines the degree of overlap of the bag stacks. Such a system provides the operator with a reasonable amount of time to unload the bag stacks for storage or removal to bag filling machinery.

Inherent disadvantages are associated with stacking tables of the above described nature. The most prominent of which is loss of stack registration during indexing of the conveyor and, in the event of stacking problems, the stack registration equipment prevents or impedes the operator in taking corrective action.

Other methods of providing the operator with sufficient time to remove a registered stack of bags involves starting and stopping the bag machine by providing a remote start and stop switch located by the stacking table. As will be readily appreciated such a method results in disadvantages. the most important of which is loss of print registration due to the attendant inertial effects occasioned by stopping and starting of the machine Moreover, the time required for the machine to come to a halt and start up is considerably in excess of time required for the operator to remove a stack of bags from the stacking table.

SUMMARY OF THE INVENTION Accordingly. it is a feature of the present invention to interrupt web development and consequently production of bags at any time selected by the operator with such interruption of web development occurring without interrupting the main drive of the bag machine. In practice it has been found that the operator can remove a stack of bags in the time required for the bag machine to produce a single bag which, when operatmg at a rate of 200 bags per minute. removal can be effected in one-third of a second or less. Other benefits derived from the present invention is the avoidance of shifts in print registration and a reduction of a seal quality occasioned by stopping and starting the bag machine as opposed to merely arresting the web development during the interruption.

In achieving the benefits described above the present invention provides a suitable electrical control which deenergizes the clutch and energizes the brake simultaneously so that web development is arrested while the drived train of the bag machine remains activated. The electrical controls disclosed with the present invention are coordinated with the mechanical elements so that when the brake is deenergized and the clutch energized. bag production is resumed at the initiation of a bagmaking cycle. This is preferably accomplished by sending a signal through an interlock switch which is controlled by a cam. At the proper time in the cycle the cam actuates the switch energizing a relay which initiates an interruption.

It is another and equally important feature of the present invention to arrest reciprocation of the seal bar during the interrupted cycle in order to prevent multiple contact of the seal bar with the film. By doing so it is not necessary, as is true of known presently commercial machines, to scrap the bag whose one margin has been subjected to multiple contacts by the seal bar.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation of a bag machine incorporating the principles of this invention;

FIG. 2 is an enlarged prospective of a portion of the bag machine shown in FIG. 1, particularly illustrating details of the seal bar structure and its relationship witha bag transporting conveyor;

FIGS. 3, 4 and 5 show, respectively, the relationship assumed by the seal bar structure during normal operation and when it is in its down position during severing and sealing of the thermoplastic web, in its raised position and when the machine has been signalled for interrupt, and when an interrupt cycle is in progress;

FIG. 6 is an enlarged fragmentary portion of FIG. 1 as viewed substantially along the line 6-6 showing cam actuated limit switches; and

FIG. 7 diagrammatically shows a portion of the seal bar and a schematic of the electrical control circuit for initiating an interrupt cycle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is related to the subject matter shown and described in the U.S. Pat. Application to Robert J. Wech filed Sept. 16, 1968, U.S. Pat. Ser. No. 760,048 and the U.S. Pat. Application to Corey T. Hook filed on Nov. 27, I968, U.S. Pat. Ser. No. 779,453. Both of these applications are assigned to the assignee of the present invention and by reference thereto it is intended that they be incorporated herein.

FIG. 1 illustrates a portion of a bag machine 10 incorporat ing the present invention. The thermoplastic web processed by the machine is indicated by the letter TW and it moves through the machine in the direction of the arrow A by draw rolls 12 shown in dotted lines. When the thermoplastic web has progressed to the point shown in FIG. 2, it has been folded and gussetted by mechanisms, the details of which are disclosed in the above Wech application. Immediately downstream of the draw rolls 12 (from right to left as viewed in FIG. 1) the web is engaged by a reciprocating seal bar structure 14 whose operation is coordinated with the intermittent movement of the thermoplastic web, and it is effective to sever and weld the web along a line transverse to its direction of movement. Upon severing of the web individual bags result and they are transported by a conveyor assembly 16 to a stacking table 18 where the bags are constrained to define a registered pile. For example, the stacking table may be provided with sheet metal fences against which adjacent margins of the bag engage to thereby produce a neatly stacked pile.

On a base plate 20 laterally spaced generally similar side frames are supported to extend vertically upwardly and are identified in FIG. 2 by the numerals 22 and 24. On the upper surface of each side frame means 26 are mounted thereon for holding the seal bar structure 14 in its raised position whenever interruption of web development is selected by the operator or automatically selected after a predetermined count by the control circuit of the machine. The means 26 comprise pneumatic cylinders 28 supplied at their head ends with pressure fluid by conduit 30 which is connected to a flow control valve 32. The flow control valve is in turn connected to an electrically operable valve 34 which upon command of the electrical circuit connects the conduit 30 to a source of pressure of air to thereby extend the piston of each cylinder 28.

Each of the cylinders 28 are provided with a projecting rod 36 having attached thereon a block 38 preferably made of nylon which is formed with an inclined surface 40 that makes contact with a complimentary inclined surface 42 formed on a block 44 rigidly connected to seal bar mounting posts 46. When the cylinders 28 are connected to the source of pressure fluid by the valve 34, the rod 36 is extended locating the block 38 under the block 44, and since the block 44 is rigidly connected to the seal bar mounting post 46, reciprocation of the seal bar is prevented. Reference to FIG. 5 will show the block 38 in position to prevent reciprocation of the seal bar structure 14. i

On command of the operator or the predetermined counting circuit cylinders 28 retract the block 38 to resume bag production. This takes place by operating the valve 34$ to connect the head of the cylinder 22s to exhaust which renders a spring within the cylinder 28 effective to retract the block 38.

While the details of the construction and operation of the seal bar structure are shown and described in the above mentioned Wech application, certain of those details will be described herein to the extent necessary to understand the disclosure of the present invention. Referring to FIG. 2 which shows the seal bar structure 14 in enlarged-prospective, it will be observed that a beam 48 extends between the mounting post &6 and each end of the beam is provided with a short stub shaft portion 50 rotatably mounted in the posts 46. A plurality of spaced thin and metal clips 52 have one end rigidly attached to the lower surface of the beam 48 and the other end secured to a seal bar 54. During normal operation the seal bar comes in contact with a seal roll 56 having each end rotatably mounted in bearings 58 (only one of which is shown) carried by the side frames 22 and 24. The thermoplastic web TW assumes a path through the bag machine bringing it between the seal roll 56 and a seal bar 54 so that upon downward movement of the seal bar, the thermoplastic web is transversely welded and severed thereby producing a bag.

After a bag has been produced by the action of the seal bar, it is transported to the stacking table 18 by the transport conveyor assembly 16. The conveyor assembly 16 comprises a series of lower belts 60 whose upper reaches move in the direction of the arrow B and are trained about an idler shaft 62. Also provided are a series of transversely spaced upper belts 64 trained about idler shafts 66 that are rotatably mounted in arms 68 keyed to an oscillating shaft 70. The shaft 70 is mounted in bearings 72 carried on the upper surface of the side frames 22 and 24. As disclosed in the above men tioned Wech application, the drived train of the bag machine includes a cam and linkage arrangement for oscillating the shaft 70, however disclosure herein is not deemed essential since such structure is not directly pertinent to the present invention.

Due to the oscillation of the shaft 70, the idler shafts 66 are also oscillated moving the belts 64 toward and away from the upper reaches of the belt 60. The bag machine is synchronized so that that portion of the thermoplastic web TW which projects donwstream (from right to left as viewed in FIG. 2) from the seal bar 54 and the seal roll 56 is gripped between the conveyors 60 and 64 immediately after the thermoplastic web has been welded and severed and the bag is thence transported to the stacking table.

Reciprocation of the seal bar structure 14 is accomplished by connecting the mounting post 46 to a push rods 74 (only one of which is shown FIGS. 1, 3--5, and FIG. 7) having secured at their lower ends a slotted block 76 rotatably mounting a roller 78 in contact with a plate cam 80 keyed to a shaft 82. The upper end of the push rods 74 are slidably received within the mounting post 46 in order to provide relative movement between the push rods and the mounting posts under certain operative conditions as will be explained presently. Rigidly attached to the push rods 74 are plates 84 that extend laterally outwardly relative to the side frame 22 and 24. Mounted to these plates are double acting pneumatic actuators 36. The actuators 86 are provided with a projecting rod 88 rigidly attached to an car 90 which is integral with the seal bar mounting posts 46.

As shown in FIG. 5, when pressure fluid is admitted to the head end of the cylinder 86, the mounting post 46 and the seal bar structure 14 carried thereby are raised above the seal roll to an extent determined by the stroke of the cylinder 86. This arrangement provides a lost motion connection between the push rods 74 and the seal bar structure 14 which is desirable when the interrupt cycle is manually or automatically initiated.

Referring now to FIGS. 3 and which illustrate, respectively, the seal bar in its down position when it makes contact with the seal roll during welding and severing of the thermoplastic web, in its raised position during indexing of the thermoplastic web between the seal roll and the seal bar and initiation of the interrupt cycle wherein the seal bar is prevented from reciprocating in its normal-manner. It should be noted that the actuators 86 fulfills the function of a fluid clamp when its rod end is supplied with pressure air by the pneumatic circuit thus holding the mounting post 46 in firm engagement with the plate 84, but as will be pointed out, the magnitude of force supplied by the actuators 86 is insufficient to prevent relative movement between the mounting post 46 and the push rods 74.

During web development, that is, during feeding of the web through the bag machine and consequent reciprocation of the seal bar structure M, the rods 36 of the actuators 28 are retracted allowing the seal bar to reciprocate in response to the rotation of the cam St). Upon initiation of an interrupt period, either by the operator or by the automatic counting system, the head end of the cylinders 28 are supplied with pressure fluid thereby locating the block 33 in the path of the block 44 which will prevent reciprocation of the seal bar structure 14. This holds the seal bar structure 14 in a raised position. FIG. 5 shows this condition and in addition shows the cam E50 presenting its minimum radius in contact with the roller 78, which is the down position of the seal bar. Locating the block 38 to make contact with the block 44 prevents reciprocation of the seal bar structure 14, however the push rods 74 continue reciprocation since they are slidably mounted in the mounting posts 46. Although the actuators 86 have air under pressure continually supplied to their rod ends springs 92 are provided to maintain the roller 78 in contact with the cam 80. Also contributing in holding the roller 73 in contact with the cam is the weight of the push rods 74. By maintaining the roller 78 in contact with the cam 80 smooth action is insured upon initiation of web development.

To arrest web development and simultaneously therewith actuate the cylinders 23 to position the block 3% to make contact with the block 84, the control circuit shown in FIG. 7 is provided. Further, to achieve smooth action on stopping and starting web development the controls are arranged so that the seal bar structure 14 does not commence reciprocation until the push rods 74 reach their highest point which is shown in FIG. Synchronizing withdrawal of the block 38 when the high dwell portion 80a of the cam 80 comes in contact with the roller 78 insures smooth start up of the seal bar by preventing relative motion between the push rod 74 and the seal bar structure 14.

In accordance with the present invention various interrupt options are available to the operator, one of which is a foot switch FS (FIG. 1) connected to the control circuit by an electrical lead MI It will be observed that the foot switch is located in the area of the stacking table 18 so that it is within easy reach of the operators foot while he is in position to manually grasp and remove a stack of bags from the stacking table 18. As will be explained in greater detail presently momentary actuation of the foot switch energizes a relay which actuates the brake and releases the clutch thereby arresting web development. Also the block 3% is positioned under the block 44 to discontinue reciprocation of the seal bar structure 14. 1f the operator so desires the interrupt time of the machine can be extended by either maintaining pressure on a foot switch or by operating a toggle switch S9 mounted in a control box 96 supported by the stacking table 1.8. Under normal conditions the interrupt time of the machine is set between 0.3 to 3.5 seconds and such interrupt time is initiated by merely tapping the foot switch. Upon expiration of the interrupt time production automatically resumes. It is also possible, and under certain conditions advantageous, to provide the control circuit with a predetermining counter operating to automatically interrupt cycle operation after a selected number of bags have been made and then resume production after the preset time delay has expired.

The portion of the bagmachine control circuit which effects interruption of seal bar reciprocation and web development is shown in FIG. 7. It is to be understood, however, that only that portion of the control circuit is shown which is relevant to the present invention. For example, the main drive motor, holepunching accessories, heater bar control and static eliminators, all of which are connected to the control circuit of the machine are not shown since they do not relate to the present invention. In FIGS 1 and 6 there is shown a shaft .97 having a reduced diameter portion 98 extending through the side frame 24. On the shaft portion 98 there are keyed cams 100 and 102 for actuating limit switches SLS and 6L8 attached to posts 104 and 106, respectively. The limit switch 5LS provides a machine-timed switching of count pulses and it has two sets of contacts, one for pulsing the totalizing counter and the other for pulsing the predetermining counter. The limit switch 6L5 also provides a machine timed pulse which insures stopping and starting of the bag machine at a certain point of its cycle to eliminate the possibility of partial draw of the thermoplastic web.

FIG. 7 illustrates the schematic circuit diagram and a fragmentary portion of the seal bar and the seal bar drive. Also mounted on the shaft 82 there is a cam 108 which is engaged by and actuates a limit switch 3LS which alternately makes contact with leads S and 207 for energizing, respectively, the clutch C and the brake B through a clutch-brake control.

. The cycle interrupt circuit shown in FIG. 7 has three basic modes of operation which can be incorporated individually or collectively as desired but for purposes of the present disclosure all three systems are shown and will be described.

Referring now to FIG. 7 it will be seen that power is supplied to the circuit portion by lines L-l and L-2. In a line 206 a foot switch FS is provided. To initiate interruption of web development when it is so desired by the operator for either one machine cycle or a greater period of time, the operator depresses the foot switch which energizes relay SCR in the line 218. This closes normally open contacts 3CR-1 in line 214 and when the limit switch 6L8 pulses down, making contact with contacts C-2, relay 2CR in line 206 is energized. Energization of relay 2CR closes contacts 2CR-3 in line 206, opens normally closed contacts 2CR-1 in line 226, and opens normally closed contacts 2CR-2 in line 250. It is to be kept in mind that cams 100 and 102 operating limit switches 5LS and 6L5, respectively continually rotate to provide a machine timed pulses for counting and for interrupting and commencing machine operation at a particular point of a bag-making cycle. Opening of contacts 2CR-l in line 226 deenergizes the clutch and maintains the brake energized thereby interrupting web development.

In addition to the energization of relay 2CR, relays 4CR, in line 212, and ITR in line 216 are energized. Energizing relay 4CR in 212 opens normally closed contacts 4CR-l in line 258, closes normally open contacts 4CR-2 in line 236 and opens normally closed contacts 4CR-2 in line 242.,Opening contacts 4CR-1 in line 248 disarms the predetermining counter circuitry while opening of normally closed contacts 2CR-2, in line 250, disarms the totalizing counter. If the operator maintains the foot switch in line 206 closed the machine remains on brake irrespective of the actuation of 6L5 by the cam 102 since, energization of the relay 2CR and a consequent actuation of the contacts related thereto, maintains the brake, schematically shown in line 246, energized. If the operator so desires, maintaining the machine on brake can be effected without holding the foot switch. This can be accomplished by merely actuating toggle switch S9 in line 208 and accordingly the machine is maintained on the brake portion of its cycle indefinitely.

Momentary actuation of the foot switch also causes energization of solenoid 110 shifting the spool in the valve 34 to thereby admit air under pressure to the cylinder 28 by the conduit 30 through the flow control valve 32. The piston rod 36 and the block 38 carried thereby are translated toward and under the block 44 thereby interrupting reciprocation of the seal bar 54. The period of time in which the block 38 remains in the seal bar interrupt position (shown in FIG. 5) is depen dent upon the setting of the time delay relay ITR in line 216. The time delay relay can be set for any reasonable interrupt time which may extend from 0.3 to 3.5 seconds. This relay is a delay on pull-in type; After the time delay period, contacts lTR open in line 210 and when the 6L8 engages contacts C2 relays ZCR, dCR and 3CR are deenergized. Slnce the valve 34 is provided with a spring return the rod 36 is immediately retracted upon deenergization of the solenoid 110 by virtue of deenergization of relay 3CR and consequent opening of contacts SCR-l in line 214. Machine operation is resumed at that point of the machine cycle where a full draw of the web can be effected. The machine, of course, then resumes its normal clutch brake operation by closing of contacts ZCR-l in line 226 occasioned by deenerigization of relay ZCR in line 206. In addition, contacts dCR-Z in line 236, MIR-2 in line 2&2 and 4CR-l in line 248 return to the condition shown in FIG. 7.

The predetermining counter is electrically connected to a capacitor 01 in line 2 32 which operates to reset the counter when relay 4CR is energized. When dCR-Z in line 236 is closed and 4CR-2 in line 242 is opened the capacitor discharges resetting the counter to its predetermined reading.

In the event one chooses to operate the bag machine of the present invention without utilizing the totalizing counter in line 250 or the predetermining counter toggle switches Stl-A in line 250 and 88-8 in line 232 are provided. It is merely necessary to actuate these toggle switches to the off position electrically disconnecting the predetermining counter and the totalizing counter from the bag machine circuit.

A predetermining counter found suitable is manufactured by SODECO and sold through LANDIS & GYR Inc. of 45 West 45th Street, New York, NY. The model number of such counter is NO. 2TCeF4PE. The clutch-brake control is made by Warner Electric Brake and Clutch Company of Beloit, Wisconsin and is identified by model number 80l6-00l-XXX.

According to the above description it can be appreciated that the bag machine of the present invention provides an apparatus which interrupts web development and reciprocation of the seal bar at any time determined by the operator or when a selected number of bags have been produced.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention as set forth in the appended claims.

We claim:

1. In a bag machine for making bags from folded or tubular thermoplastic web by intermittently feeding and severing the web by a seal bar structure, including a seal bar which is rendered inactive when web movement is momentarily interrupted,'said machine comprising means for actuating the seal bar, and means for interrupting actuation of the seal bar while maintaining operation of said seal bar actuating means, and wherein said seal bar interrupting means maintains said seal bar in a location spaced from the thermoplastic web so that damage to the web is prevented.

2. In a bag machine for making bags from folded or tubular thermoplastic web by intermittently feeding and severing the web by a seal bar structure, including a seal bar which is rendered inactive when web movement is momentarily interrrupted, said machine comprising means for actuating the seal bar, and means for interrupting actuation of the seal bar while maintaining operation of said seal bar actuating means, and wherein said seal bar interrupting means comprises means engageable with the seal bar structure for holding the seal bar in a raised position.

3. The bag machine according to claim 2 wherein said seal bar engaging means includes means for actuating said engaging means to effect interruption of said seal bar.

4. The bag machine according to claim 3 wherein said actuating means comprises a fluid cylinder, and means are provided for activating said actuator in synchronism with the bag machine drive.

5. An apparatus for maki'ngbags from folded or tubular thermoplastic web material comprising a seal bar apparatus for transversely sealing and cutting an intermittently fed ther moplastic web with said sealing and cutting occurring during a momentary repose period of such web; means, including cams and associated push rods, for reciprocating said seal bar apparatus; said seal bar apparatus comprising seal bar supporting members slidably mounting on the respective upper portions of said push rods; .fluid clamps for holding said supporting members against slidable movement relative to said push rods, and means for preventing reciprocation of said seal bar with said push rods while said fluid clamps are supplied with pressure fluid and said cams continue to reciprocate said push rods.

6. The apparatus according to claim further comprising control means operated in time relation with said push rod actuating cams for initiating. reciprocation of said seal bar with said push rods when said cams have displaced said push rods to their upper position and thereby commence seal bar operation at the beginning of a bag-making cycle.

7. The apparatus according to claim 6 wherein said control means include means for interrupting web movement and seal bar reciprocation at the will of the operator or when a predetermined number of bags have been produced.

8. A seal bar structure for a bag-making machine of the type which produces bags from folded or tubular thermoplastic web material, said structure comprising elongate push rods, cams for reciprocating said push rods in unison, posts slidably receiving the upper end portions of said push rods, a seal bar extending between and supported by said posts, fluid clamps for holding said posts against slidable movement relative to said push rods, outwardly extending ledges rigidly secured to said posts, and means selectively or automatically located to engage said ledges to prevent reciprocation of said posts and accordingly said seal bar while reciprocation of said push rods continues.

9. In a bag machine for making bags of folded or tubular thermoplastic web material comprising means for intermittently feeding the web material a desired amount, a reciprocating heated sea bar extending transversely to the direction in which the web is fed for sealing and severing the web at selected longitudinally spaced intervals, a drive mechanism for feeding the web material and reciprocating said seal bar, and means operable after a predetermined number of machine cycles or at the will of the operator for interrupting operation of said seal bar and said web-feeding means for at least one machine cycle while maintaining operation of the drive mechanism.

10. The bag machine according to claim 9 wherein said interrupting means includes means for terminating and initiating bag machine operation at the end and at the beginning, respectively, of a bag-making cycle.

11. In a bag machine of the type wherein a feeder intermittently advances a thermoplastic web under a reciprocating seal bar, with drive means for the feeder and seal bar; the improvement wherein said seal bar drive means comprises a normally continuously running driving element for the seal bar, a composite reciprocable driven element with one part operated by the driving element and the other part connected to the seal bar, coupling means for normally causing said driven element parts to reciprocate together for reciprocating said seal bar, interrupter means for holding the driven element part connected to said seal bar against reciprocation when the seal bar has been lifted from the web, said coupling means accommodating continued reciprocation n of the other driven element part by said driving element, and means for actuating said interrupter means.

12. The bag-making machine of claim 11, wherein said driv ing element for the seal bar comprises a rotating cam, said means for actuating the interrupter means including a selectively energized control synchronized with said web feeder.

13. The bag making apparatus of claim 12 wherein said selectively energized control for said interrupter actuating means comprises a completed bag counter.

M, The apparatus of claim ill wherein said coupling means for the driven element parts comprises a fluid cylinder assembly normally pressurized to couple the parts, said interrupter means holding said driven element against the pressure in said fluid cylinder assembly.

15. The apparatus of claim 14 wherein said fluid cylinder is double acting, and manually controllable means for pressurizing said fluid cylinder assembly to move the seal bar part of said driven element to withdraw the sealbar from the web.

16. A bag machine for making bags from tubular or folded thermoplastic web comprising a platen underlying the web; a heated reciprocating seal bar engageable with said platen; drive means for coordinating intermittent feeding said web and reciprocation of said seal bar; said seal bar making contact with said platen when the web is momentarily at rest thereby transversely severing and sealing the web; means, operable after a predetermined number of machine cycle or at the will of the operator, for interrupting bag-making for at least one machine cycle; and means, effective during the interrupt period, for preventing said seal bar from contacting the web which thereby prevents heat damage to the web.

CERTIFICATE OF CORJ'UECTION FD-IOSO fs/ss} Patent 140 3,541,929 Dated A t 9, 1971 Inventor) DONALD c. CRAWFORD et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

301. 2, line 22, after "1968" delete "U.S.' Pat. line 24, befc "Ser. No. delete "U.S. Pat. t

line 50, before "push" delete "a"; line 59, change "fra to frames Col. 5, line 54, change "258" to 248 Col. 7, line 40, change "sea" to seal Col. 8,'line 17, after "reciprocation" delete "n.".

Col. 3,

Signed and sealedithis 28th dey of December 1971 (SEAL) Attest:

ROBERT GOTTSCHALK EDWARD 'M.FLETCHER,JR.

Acting Commissioner of Patents Attesting Officer 

